Electromechanical Assembly for Routing Electrical Signals in Guns for Well Perforation

ABSTRACT

An electromechanical switch for use in well perforating gun assemblies wells comprising an initial pass-through configuration where the switch passes an electrical connection from a shooting line through the switch&#39;s plunger to the neighboring gun until a pressure event acts on the switch causing the shooting line to disengage from the neighboring gun and connect to the internal detonator for subsequent firing sequence to trigger detonation.

BACKGROUND OF THE INVENTION Field of the Invention

This invention refers to an electro-mechanical switch assembly for routing electrical signals in a plurality of well perforating guns (“guns”). This switch assembly isolates a single gun's explosive detonator from a common firing signal line shared by the plurality of guns until mechanical action from a neighboring gun causes a switching action removing the isolation thus preparing the gun to trigger on a following fire signal.

This process of well perforation consists of the perforation of the metallic casing of a well, of isolating cement surrounding the casing, and of the layers of rock in the producing formation by means of explosives housed within perforating guns; achieving, through bore holes produced by a plurality of charges, a connection between the depths of the producing zone and the interior of the well. While this invention is generally found in the petroleum production industry, it may be equally applied to other environments where perforation of well casing into the surrounding environment is necessary, such as water wells.

Background of the Invention

The perforation of producing wells is realized by lowering into the well a perf assembly comprised of a plurality of guns each containing a plurality of charges. The guns are connected end to end and wired in sequence to a firing circuit on the surface of the by intermediate subs containing pass through openings for wiring. A firing wire, coupled with the casing as a ground, carries an electrical signal through the well bore to connect with each gun and allow firing of the detonators

One method of independently firing the guns is to use individually addressable detonators such as those described in U.S. Pat. No. 8,091,477 and U.S. Pat. No. 8,230,788. Another method of independently firing the guns is to connect each gun through a pressure sensitive switch which grounds the detonator of each gun until the pressure of the previous gun's firing triggers the switch to an active state.

Diodes are used to cause each gun to require a polarity reversal from the signal which fired the previous gun. This prevents the signal from propagating throughout the assembly as the blasts set each pressure switch sequentially, and the pressure switches prevent the later guns from firing before the previous ones. This method requires a continuous electrical signal to run the length of the perf assembly.

The preferred method is to fire the farthest/lowest gun first. Then, sequentially fire each gun back toward the well opening. This is because the explosion/pressure/debris from the gun's firing can possibly damage adjacent guns. Wires can break or connectors can loosen during shockwave vibrations, or by blast force. With pressure switches, any damage retrieval of the perf assembly for correction, as the rest of the assembly is now non-fireable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and B are wiring diagram of a press before and after experiencing a mechanical pressure action.

FIGS. 2A and B show a cross section of a common pressure switch currently used in the industry.

FIGS. 3A and B show cross sections a push spring pressure switch in accordance with an exemplary embodiment of the innovation.

FIGS. 4A and B show cross sections a pull spring pressure switch in accordance with an exemplary embodiment of the innovation.

DETAILED DESCRIPTION OF THE INVENTION

the purpose of the pressure switch is to allow a single fire signal wire to control a plurality of guns in a managed sequence. This is accomplished by integrating a pressure switch into each gun's detonation line. The switch passes the fire signal along to the next gun in the sequence so that only the last/farthest/lowest gun in the sequence response to the signal by detonating.

The detonation of the lowest gun in the sequence causes a mechanical pressure on the neighboring gun which changes the position of the pressure switch so that the switch no longer passes the fire signal along, but instead routes it internally to the detonator. A diode connected in series with the detonator prevents the fire signal from propagating through all the guns by requiring each gun to use a reverse polarity signal from the neighboring guns.

The applicant has improved switch designs by introducing extra protection for the interior of the switch so that debris from the neighboring explosions do not foul electrical contacts. Locking components ensure the switch stays in an initial pass-through configuration until significant pressure is applied, and the integration of springs bias the switch to an internal routing configuration once triggered to ensure it remains in a desired position. Additionally, compression springs between the toggle and the piston ensure a reliable electrical contact for the switch's pass-through configuration.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. A and B are wiring diagram of a pressure switch before and after experiencing a mechanical pressure action. FIG. 1A is a wiring diagram of a switch (100) in an initial configuration. The toggle (140) extends from the common point C to connect to point A. This is the pass-through configuration so the fire signal from the shooting line (110) leading to the surface passes through to the next gun via the down-hole contact (120).

FIG. 1B is a wiring diagram of the same switch (100′) after a pressure event. Pressure from an explosion in the neighboring gun (to the right) causes the piston (150) to move the toggle (140) from point A to point B. The toggle (140) extends from the common point C to connect to point B. This is the internal routing configuration. So the fire signal from the shooting line (110) from the surface is now routed to the local gun (130). A diode (133) wired in series blocks the fire signal from reaching the detonator line (135) until the proper polarity is supplied.

FIGS. 2A and B show a cross section of a common pressure switch currently used in the industry. In a normal industry pressure switch (200) the toggle (140) is actually a metallic slide held by insulating material (230) against the piston (150) which is also metallic and acts as the pass-through connection (120) to the neighboring gun. The piston (150) is secured in an ended position (210) with a plastic sleeve (155) and an O-ring (220).

FIG. 2B shows the desired position of the switch components after pressure is applied to the piston (150). The piston is pushed back (210′) to a new position and causes the toggle (140) to separate and contact point B, a metallic sleeve. This completes the electrical circuit of the shooting line (110) to the local gun (130) so the fire signal will be routed to the diode (133) and the detonator (133).

However, problems can develop if the toggle (140) is not sufficiently contacting the pass-through contact/piston (120/150) because the fire signal will not be conducted to the downhole guns, resulting in a misfire. If the pressure does not produce sufficient force to move the toggle (140) back into the pressure switch body to connect with the metallic sleeve (B), or mechanically bounces off the bottom of the switch, the toggle can fail to maintain contact with the local gun (Point B) resulting in a misfire.

FIG. 3A and B show cross sections of a push spring pressure switch in accordance with an exemplary embodiment of the innovation. In this configuration, the plastic sleeve (155)'s O-ring (220) is supplemented with a second O-ring (320). The double O-ring configuration causes a pressure reduction the secondary O-ring by the shielding of the first O-ring reducing the chance of contaminating water and debris from entering the switch's inner compartment. A beveled edge (310) provides an additional level of protection because light pressure forces the bevel closed until the point of failure where the bevel ring snaps away from the plastic sleeve causing an outward force away from the O-rings.

The toggle (140) has a spring (330) at the top end to maintain contact with the piston (150) when the toggle is in the initial position to prevent misfire. Internal threads (340) hold the toggle in the initial position so that the pass-through connection is assured. Pressure from an explosion in the neighboring gun (to the right) causes the piston (150) to move with the triggering force necessary to break the bevel ring (310) of the plastic sleeve and the internal threads (340) of the toggle.

An internal spring (350) biases the toggle to move from point A (not indicated) to point B. The toggle (140) in the internal configuration holds the electrical contact (point B) against the internal pressure ring (360). This internal routing configuration is held by the internal spring (350) against later shifting or bounce so the fire signal from the shooting line (110) from the surface is now reliably routed to the local gun (130) and misfire is prevented.

FIGS. 4A and B show cross sections of a pull spring pressure switch in accordance with an exemplary embodiment of the innovation. In the alternative configuration, the internal spring (370) is secured in an extended configuration to one end of the switch (380) so it creates a pulling force to urge the toggle (140) away from the internal threads (340) and disengage the spring connecting the toggle (140) to the piston (150). The internal spring (370) provides sufficient tension to ensure the toggle (140) remains in contact with the electrical contact (point B) by pressing against the internal p g (360). This internal routing configuration is held by the internal spring (370) against later shifting or bouncing so the fire signal from the shooting line (110) from the surface is not reliably routed to the local gun (130) and misfire prevented.

As in the previous embodiment, the toggle (140) has a spring (330) at the top end to maintain contact with the piston (150) when the toggle is in the initial position to prevent misfire. Internal threads (340) hold the toggle in the initial position so that the pass-through connection is assured. Pressure from an explosion in the neighboring gun (to the right) causes the piston (150) to move with the triggering force necessary to break the bevel ring (310) of the plastic sleeve and the internal threads (340) of the toggle.

In the preferred embodiments the plastic utilized is a thermoplastic polymer called Polyether ether ketone (commonly referred to as PEEK) due to its resistance to harsh chemicals and mechanical strength as well as a hydrolysis resistance to the watery environment normally found in drilling. One skilled in the arts would appreciate that other materials of plastic, glass, or metal may be utilized as well as different mechanical configuration such as sheer points or break-aways for the threads and bevel to determine the breaking points necessary to trigger the switch at the desired pressures.

The diagrams in accordance with exemplary embodiments of the present invention are provided as examples and should not be construed to limit other embodiments within the scope of the invention. The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications. 

What is claimed is:
 1. An electromechanical switching assembly comprising: a switch body having a first contact for electrically connecting to a shooting line; the first contact being slideably mounted within the switch body and being electrically connected to a second contact, the second contact being slideably mounted within the switch body and protracted from one end of the switch body forming a plunger sensitive to pressure of a predetermined threshold; pressure causing the second contact to retract into the switch body, transferring movement to the first contact which disengages from the second contact and electrically connects to a third contact.
 2. The assembly of claim 1 wherein the first contact has a compression spring extending to the second contact to maintain electrical connection between the two contacts.
 3. The assembly of claim 1 wherein the second contact is encircled by a flexible/compressible O-ring fitting inside one end of the switch body and preventing leakage therebetween.
 4. The assembly of claim 3 wherein the second contact is encircled by a second flexible/compressible O-ring fitting inside one end of the switch body behind and spaced apart from the first O-ring and preventing leakage therebetween.
 5. The assembly of claim 1 wherein the second contact is urged by a spring toward the third contact, the spring held in a compressed state until the threshold pressure is applied.
 6. The assembly of claim 5 wherein the spring is held in a compressed state by a threaded portion of the contact screwed to the housing of the switch, the threads breaking under the threshold pressure and freeing the first contact to be moved by the spring.
 7. The assembly of claim 5 wherein the spring is held in a compressed state by a beveled portion of the second contact being greater than the inside of the switch body and mating with a beveled opening at one end of the switch body.
 8. A method of electrically connecting a plurality of perforating gun assemblies wherein a shooting line is connected to a switch in the first gun, the switch being configured to pass an electrical signal from the shooting line to the second gun's shooting line through a plunger; the plunger reacting to pressure from an explosion in the second gun, disconnecting the shooting line from the second gun and an internal spring urging the shooting line to connect to the first gun's internal detonator.
 9. The method as described in claim 8 wherein the plunger comprises a compression spring between the shooting line and the back end of the plunger to ensure electrical contact until the pressure reaction.
 10. The method as described in claim 8 wherein the plunger comprises a threading joint holding a spring in compression until a pressure threshold breaks away the thread allowing the spring to reconnect the shooting line to the first gun's detonator. 